Windows 7 inbuilt tool BitLocker Drive Encryption is a great tool to protect your data from loss, theft, or hackers.
You can enable / disable BitLocker for any particular drive. Once BitLocker is turned on, any file you save on that drive is encrypted automatically. Thus it helps keep everything from documents to passwords safer by encrypting the entire drive .
Bitlocker is available in only two editions of windows 7:
Bitlocker is not available for other windows 7 editions: Starter, Home Premium, Professional.
So, you CANNOT enable Bitlocker on windows 7 professional. Premium and starter editions.